In PowerMail, a "mailable" member is one whom:
- has an email address
- is not marked as having a Bad email address (email hasn't bounced)
- has not unsubscribed from all mailings
When you Publish a PowerMail, you will be shown an estimate of the number of mailable members who will receive the message. A number of factors can lower your actual sent count from the estimate. These include:
- Closed accounts. Some emails may bounce. This can happen because a student has left a school, an employee has moved to a new job, or a person switched from, e.g., Outlook to Gmail.
- Bad email addresses. A member may have an email that is superficially correct, but still not valid. For example, email@example.com. You can easily recognize that this is probably supposed to be firstname.lastname@example.org, but it's a valid email address as far as a computer is concerned. If there's no such domain as outlool.com, email will not be able to be sent to the member. It can't even bounce, because there's no server at outlool.com to say it's an invalid account!
- Temporary account issues (soft bounce). A mail server may be down for maintenance, experiencing technical difficulty, or be currently too overloaded to accept more email. Although it's less common these days, a mailbox may be too full to accept more email.
- Reputation issues. Receiving servers may score your message as spam.
Do not expect all of your PowerMail recipients to receive your email instantly! As email users, most of us are used to our recipients receiving our emails in just a few seconds when we send from our private email accounts. It seems instant, but bulk email exposes that it's not quite instant, and the small amount of time it takes to send a message adds up to a noticeable amount of time as the number of recipients increases:
- Email servers can only send or receive emails on several "channels" at a time, depending on how memory and processors are used. For example, if you send to 10,000 people, they may be at 3,000 domains. The sending server can't send to all 3,000 domains at the same time. This means messages are queued up and have to wait their turn to go out on a channel. Additionally, there is a little overhead in queuing all those messages. A good analogy for this is a bridge. It only has a certain number of lanes. If you want to get across the river, you've got to get in a lane. There's no delay during off-peak times, but during rush hour... You wait!
- The sending email server has to connect to the receiving email server. If the receiving email server is very busy, it can be difficult to connect, or to get enough connections to send lots of messages simultaneously.
- The sending and receiving servers carry on a "conversation" to pass the email along. Although the conversation happens at computer speeds, each message takes its fraction of time, and this becomes more noticeable when there are large numbers of recipients at the same domain (e.g., aol.com).
- The Internet "routes" the conversation between the sending and receiving servers. Sometimes a route can be slow or damaged, slowing everything down.
- Receiving email servers often set limits to how fast they'll allow a server to send them email. This is especially true of the major web based email providers, such as Yahoo, Outlook/Hotmail/MSN, Gmail, and AOL, who are constantly receiving staggering numbers of emails. The providers receiving the majority of your emails are also the ones most likely to limit the pace of sending. When a receiving server asks our server to wait a while before sending more emails, our server will try again every two hours, for up to two days, to send the message.
- Receiving email servers can be so overloaded that they aren't currently taking any emails at all. An email server in this state will ask the sending server to "call back" later. Again, our server will try every two hours, for up to two days, to send the message.
- Technical difficulties can also cause delays in sending a message. Yahoo, for example, has had a relatively bad record for being down due to technical problems within their email infrastructure.
The typical pattern when sending a mailing is that most of the recipients get the message within a few minutes. Beyond that, the speed slows down as the remaining recipients become concentrated at AOL, Gmail, Outlook, Yahoo, or other major email providers. These emails are waiting their turn for delivery to the providers most likely to be overloaded or limiting the speed at which they'll accept email. Other stragglers tend to be servers that are having problems, as described above.